Our brain, although it is asleep and inventing new worlds in our dreams that are not related to the tranquility of our room and our bed, continues to record everything that happens around it , according to the conclusions of a team of researchers from the Cognitive Sciences Laboratory and Psycholinguistics of France and collected by the journal Current Biology.
To better understand how the brain protects itself from outside influences, the researchers invited 18 participants for a morning nap in the lab (which is prolific in dreams). Remember that dreams occur mainly during what is known as REM phase, since the brain is in some way in a waking state during this phase of sleep, showing brain activity similar to that of an awake person. The body, on the other hand, is paralyzed, though not entirely. During certain phases of REM sleep, the eyes continue to move. Research has shown that such movements are related to dreams.
Sleep is divided into two distinct phases: non-rapid eye movement sleep (NREM), in which the brain slows down and where dreams are more infrequent and less complex, and rapid eye movement sleep, in which sleepers They appear to be sound asleep, but their brain activity resembles waking activity and their eyeballs can move frantically behind their closed eyelids, as if sleepers are exploring an inner world.
To study how the dreaming brain interacts with external sounds, the scientists managed to put this group of volunteers to sleep while listening to stories in French mixed with nonsense language. By combining the EEG with a machine learning technique, they confirmed that even when the brain was asleep, it continued to record everything that was happening around it. They also showed that, during light sleep, the brain prioritized meaningful speech, just as it does when it is in a waking state. However, this is actively filtered during the eye movement phases of REM sleep. In other words, our sleeping brain can select information from the outside world and flexibly amplify or suppress it , depending on whether or not it is immersed in a dream.
The study therefore found that sleepers actively suppress important information every time the eyes move during the rapid eye movement (REM) phase, such as the sound of conversation, during the sleep phase. Thus, this ability to prioritize relevant and meaningful information was stopped and reversed each time eye movements were recorded. This reversal suggests a critical shift in the way we process our surroundings when we dream in favor of more complete isolation from the outside world.
Why is this relevant? Because eye movements in REM sleep generally mark the occurrence of dreams, clarifies Thomas Andrillon, researcher and sleep expert at the Turner Institute for Mental and Brain Health at Monash University and a co-author of the work.
And the team believes that this mechanism allows the brain to protect the sleep phase, which is necessary for emotional balance and consolidation of the day’s learning. Although dreams are predominant during periods of eye movement, they can also occur during other phases of sleep.
“Isolating ourselves from our environment could have significant advantages in terms of consolidating memory, emotional balance, and ensuring that we wake up each morning fresh and ready to face a challenging world – and a very real one,” the authors conclude.
Referencia: Matthieu Koroma, Célia Lacaux, Thomas Andrillon, Guillaume Legendre, Damien Léger, Sid Kouider. Sleepers Selectively Suppress Informative Inputs during Rapid Eye Movements. Current Biology, 2020; DOI: 10.1016/j.cub.2020.04.047
